The present invention relates to a method of making a surgical splint as an aid to the positioning of a tooth-carrying maxillary segment which is to be mobilized following Le Fort I surgery.
More particularly it relates to such a method in accordance with which a maxillary cast and a mandibular cast of a pair of casts of the patient made at least approximately in the ratio 1:1 are centered in an articulated manner in an articulator with reference to the jaw hinge and are thereby adjusted into the pre-operative dental position, the maxillary cast is mobilized, the mobilized maxillary cast is adjusted three-dimensionally in the articulator into the desired post-operative dental situation relative to the pre-operative planned position of the upper lip of the patient and relative to the rest of the pair of casts, and on the basis of the relative adjustment of maxillary cast and mandibular cast achieved according to the preceding step the surgical splint is made in a gap between maxillary cast and mandibular cast for analogous intra-operative use.
One method of this type is disclosed for example in the German reference DE 4,018,273 A1. In this method the adjustment of the mobilized tooth-carrying maxillary segment 30 takes place in a manner known per se, after a Le Fort I model operation has been carried out.
In maxillary orthodontic-surgical treatment, after the Le Fort I osteotomy, a three-dimensional readjustment of the maxilla is possible. The maxilla of the patient is positioned in the new position by means of a surgical splint and is fixed with osteosynthesis wires or with mini-plates. During the treatment planning, during the cast surgery and during the surgery itself it is particularly important to maintain an exact position of the upper incisors in relation to the upper lip and to maintain an exact position of the whole maxilla in relation to the rest of the skull including the jaw hinge (Harle, F., Le Fort I ostectomy (using miniplates) for correction of the long face. J. Oral Surg. 38: 427-432, 1980; Zurcher A., Hardt N., Steinhauser, E. W., Interokklusaler Splint als Rezidivprophylaxe bei totalen Unterkieferosteotomien. Fortschr. Kiefer Gesichtschir. 26: 81-82, 1981; Ellis E., Modified splint design for two-jaw surgery. J. Clin. Orthod. 16: 619-622, 1982; Ripley, J. F., Steed, D. L., Flanary C. M., A composite splint for dual arch orthognathic surgery. J. Oral Maxillofac. Surg 40: 687-688, 1982; Turvey, T. A., Hall, D. J., Fish, L. C., Epker, B. N., Surgical-orthodontic treatment planning for simultaneous mobilization of the maxilla and mandible in correction of dentofacial deformities. Oral Surg. Oral Med. Oral Pathol. 54: 491-498, 1982; Luhr, H. G., Miniplate fixation of Le Fort I osteotomies. (Discussion to Rosen, H. M.). Plast Reconstr. Surg. 78: 755, 1986; Somsiri, S. T., Das Doppelsplintverfahren zur Vorbereitung einer simultanen chirurgischen Lagekorrektur des Ober- und Unterkiefers. Fortschr. Kieferorthop. 48: 59-66, 1987; Bell, W. H.; Mannai, C., Luhr, H. G., Art and science of the Le Fort I dolfracture Int. J. Adult Orthod. and Orthogn. Surg. 33: 23-52, 1988; Lindorf, H. H., Osteosynthese durch Schrauben und Miniplatten bei kieferorthopadischen Operationen. Inf. Orthod. Kieferorthop. 3: 329-350, 1988; Luhr, H. G. and Kubein-Meesenburg, D., Rigid skeletal fixation in maxillary osteotomies. Intraoperative control of condylar position. Clin Plast. Surg. 16: 157-163, 1989; Paulus, G. W., Moderne funktionelle und asthetische Aspekte bei kieferorthopadischen Operationen. Inf. Orthod. Kieferorthop. 22: 33-55, 1990; Wangerin, K., Einzeitige bimaxillare Korrektur extremer Fehlbisse-Vorbehandlung, Planung und Operationsmethode mit funktionsstabiler Fixierung im Ober- und Unterkiefer. Dtsch. Z. Mund. Kiefer Gesichtschir. 14: 424-432, 1990; Luhr, H. G., Schwestka, R., Kubein-Meesenburg, D., Intraoperative control of condylar position in maxillary osteotomies with rigid skeletal fixation. In: Bell W. H. (Hrsg): Modern practice in orthognathic and reconstructive surgery. Saunders, Philadelphia, at press).
First of all, in accordance with the preoperative planning, the cast surgery is carried out (Bell W. H., Proffit, W. R., White R. P., Surgical correction of facial deformities. 234-441, Saunders, Philadelphia, 1980; Epker, B. N., Fish, L. C., Dentofacial deformities. Integrated orthodontic and surgical correction. Mosby, St. Louis, 1986; Ehmer, U., Rohling, J. Dorr, K., Becker, R., Calibrated double split cast simulations for orthognathic surgery. Int. J. Adult Orthod. Orthognath Surg. 33: 223-227, 1988; Janson, I. and Steinhauser, E. W., Kieferorthopadische Chirurgie - Eine interdisziplinare Aufgabe. Quintessenz, Berlin, 1988; Jung, D., Datentransfer zwischen Artikulator und FRS zur Erstellung von diagnostischem Set up und VTO im komplexen Behandlungsfall. Inf. Orthod. Kieferorthop. 3: 383-395, 1988; Proffit, W. R. and White, R. P., Jr., Surgical-orthodontic treatment. Mosby, St. Louis, 1991). It is important, initially in a first articulator, to determine the exact pre-operative position of the maxilla and then in a second articulator to position exactly the desired post-operative position, since in accordance with the position in the second articulator the surgical splint is made with which in the surgical process the tooth-carrying maxillary segment is positioned in the planned position. Therefore, the cast or model surgery requires the greatest possible accuracy. Measurements with a ruler and the marking of reference points and reference lines on the base of the plaster cast above the tooth line of the maxilla model as well as the making of saw cuts in the base corresponding to these lines have not proved to be sufficiently accurate methods for the positioning of the maxillary segment. This is particularly so when the tooth-carrying maxillary segment has to be readjusted in several dimensions at the same time (Ellis, E. III., Accuracy of model surgery: Evaluation of an old technique and introduction of a new one. J. Oral Maxillofac. Surg. 48: 1161-1167, 1990). Therefore, various devices for the controlled adjustment of individual reference points on the teeth of the maxillary cast have been developed.
From the particularly eminent prior publication by Ellis E., III, Gallo, W. J., "A Method to Accurately Predict the Position of the Maxillary Incisor in Two-jaw Surgery", J. Oral. Maxillofac. Surg. 42: 402-404, 1984, a method for the exact positioning of one cutting edge of the upper incisors in the articulator in the sagittal-vertical plane is known, in which before the cast surgery a wire is wound around the incisal pin of the articulator in which the cast surgery is to be carried out, with the wire tip contacting the incisal edge of an upper incisor of the maxillary cast. This wire can be moved to one side during the cast surgery and then be repositioned thereafter in its final position. The distance between the tip of the wire and the new position of the edge of the upper incisor indicates the displacement of the incisor. This method is of limited use, because the wire tip is only adjusted to the pre-operative situation.
From the likewise eminent prior publication by Schwestka, R., Engelke, D., Zimmer, B., Kubein-Meesenburg, D., entitled "Positioning control of the upper incisors in orthognathic surgery. Pre-operative planning with the Model Positioning Device and intra-operative application of the Sandwich Splint", Eur. J. Orthodont. 13 367-371, 1991, another method is known. In this method, in the articulator, a measuring element is adjusted in a controlled manner in three dimensions with a model positioning unit to the pre-operative and also to the planned post-operative position of one incisal edge of a central incisor of the maxillary model. The relative spatial coordinate of each setting can be read off from scales.
Other authors have described methods used in cast surgery for the measurement successively in time of several different reference points on the teeth of the maxillary cast. These include on the one hand the use of a modified Boley measuring instrument in the articulator (Henry, C. H., "Modified Boley Gauge for use as a Reference Plan in Orthognathic Surgery", J. Oral Maxillofac. Surg. 48: 535-539, 1990), and on the other hand repeated shifting of the maxillary model on the Erickson measuring table outside the articulator (Ellis, E. III., "Accuracy of Model Surgery: Evaluation of an Old Technique and Introduction of a New One", J. Oral Maxillofac. Surg. 48: 1161-1167, 1990). The latter publication makes it clear that by the choice of reference points on the teeth of the maxillary model, on geometrical grounds the tolerance limits for positioning errors can be significantly reduced in comparison to the use of reference points on the base of the maxillary model.
During the surgery the planned position of the maxillary model is transferred to the skull. The position in the sagittal and transversal dimensions is determined by the surgical splint. The vertical dimension requires additional controls. Different authors develop different intra-operative methods for the exact adjustment in the vertical dimension (Austermann, K. H., and Bollmann, F., Eine Methode zur Bestimmung der gunstigsten Osteotomieenbene bei Le-Fort-I-Osteotomien. Fortschr. Kiefer. Gesichtschir. 26: 121-123, 1981; Turvey, T. A., Simultaneous mobilization of the maxilla and mandible: Surgical technique and results. J. Oral Maxillofac. Surg. 40: 96-99, 1982; Johnson, D., Intraoperative measurement of maxillary repositioning: An ancillary technique. Oral Surg. Oral Med. Oral Pathol. 60: 266-268, 1985; Nishioka, G. J., and Van Sickels, J. E., Modified external reference measurement technique for vertical positioning of the maxilla. Oral Surg. Oral Med. Oral Pathol. 64: 22-23, 1987; Neubert, J., Bitter, K., Somsiri, S., Refined intraoperative repositioning of the osteotomized maxilla in relation to the skull and TMJ. J. Cranio-Max-Fac. Surg. 16: 8-12. 1988; Kahnberg, K-E., Sunzel, B., Astrand, P., Planning and control of vertical dimension in Le Fort I osteotomies. J. Cranio-Max-Fac. Surg. 18: 267-270, 1990). Clinical investigations into the question of the exact adjustment of the tooth-carrying maxillary segment in the vertical dimension show deviations between the pre-operative planned position and the intra-operative position actually achieved (Stanchina, R., Ellis, E., III, Gallo, W. J., Fonseca, R. J., A comparison of two measures for repositioning the maxilla during orthognathic surgery. Int. J. Adult. Orthod Orthognath. Surg. 33: 149-154, 1988; Van Nickels, J. E., Larsen, A. J., Epker, B. N., Predictability of maxillary surgery: A comparison of internal and external reference marks. Oral Surg. Oral Med. Oral Pathol. 61: 542-545, 1986). For these reasons, intra-operative positioning methods for a controlled three-dimensional adjustment of the tooth-carrying maxillary segment have been developed, by the use of a "sandwich splint" (Schwestka, R., Engelke, D., Kubein-Meesenburg, D., Luhr, H. G., Control of vertical position of the maxilla in orthognathic surgery: clinical application of the sandwich splint. Int. Adult Orthod. Orthognath. Surg. 5: 133-136, 1990; Schwestka, R., Rose, D., Kuhnt, D., Walloschek, W., Splint for controlling vertical position in maxillary osteotomies. J. Clin. Orthod 24: 427-431, 1990; Schwestka-Polly, R., Engelke, D., Kubein-Meesenburg, D., Luhr, H. G., Bedeutung der Vertikaldimension bei kieferorthopadischchirurgischen Eingriffen im Oberkiefer. Quintessenz 42: 595-601, 1991), or by the use of a "3D double splint method" in combination with a "Condylar positioning appliance (Schwestka, R., Engelke, D., Kubein-Meesenburg, D., Condylar position control during maxillary surgery: the condylar positioning appliance and three-dimensional double splint method. Int. J. Adult Orthod. Orthognath. Surg. 5: 161-165, 1990; Schwestka-Polly, R., Engelke, D., Kubein-Meesenburg, D., Gelenkorienteierte Einstellung des Oberkiefers mit der "Condylen-Positionierungs-Apparatur" im Rahmen der kieferorthopadischen Chirurgie. Quintessenz 42: 1099-1107, 1991). Both intra-operative methods are based upon the fact that the vertical position of the mandible in relation to the skull above the osteotomy plane is accurately reproducible in the pre-operative and post-operative situations. The vertical position of the mandible can be controlled intra-operatively with a pair of dividers. At this position of the mandible the tooth-carrying maxillary segment is adjusted three-dimensionally by means of the surgical splint as planned beforehand. Consequently, the position of the tooth-carrying maxillary segment planned during the cast surgery can be transferred exactly in three dimensions in a controlled manner during the actual surgical process. After the surgery the mandible is rotated up into the new intercuspidation position.